An important factor in regulating eNOS activity is its localization. It has been demonstrated that the plasma membrane is the most efficient location for eNOS to produce NO in endothelial cells. Further, many studies have shown that HSP90 plays an important role in increasing eNOS mediated NO generation. However the molecular mechanisms by which eNOS-HSP90 interactions are stimulated are not fully understood. Beta arrestins are ubiquitous multifunctional adaptor proteins of G-protein coupled receptors (GPCR). Beta arrestin 2 has recently been shown to bind to HSP90. However, the role of beta arrestins in regulating HSP90-eNOS interactions has not been resolved. Our preliminary data indicate that a ternary complex of beta arrestin 1 or 2, HSP90 and eNOS is formed by calcium activating agents and is attenuated by calcium inhibiting agents. Overexpression of either beta arrestin or beta arrestin 2 results in higher NO production and lower eNOS-derived superoxide generation while the double knockdown of beta arrestin 1&2 expression attenuates NO production and augments eNOS-derived superoxide generation. These data have led us to form the hypothesis that beta arrestin promotes eNOS-HSP90 complex formation in the membrane by mediating the membrane translocation of HSP90. Oxidative stress mediates the pathogenesis of many cardiovascular diseases. Our preliminary data indicate that oxidative stress decreases the expression of beta arrestin. Its expression is decreased in our shunt model of pulmonary hypertension. We have previously shown that in these lambs, eNOS is uncoupled as evidenced by eNOS HSPO interactions are reduced, superoxide generation is enhanced. We hypothesize that a decrease in beta arrestin expression contributes to eNOS uncoupling in pulmonary hypertension. It has been shown that overexpression of CuZnSOD attenuates endothelial injury but the exact mechanisms of such protection remain unclear. Our preliminary data show that overexpression of SODl increases beta arrestini expression, enhances eNOS-HSP90 interactions and increases NO production and beta arrestini expression is increased in lambs treated with SODL We hypothesize that eNOS uncoupling can be restored by SODl overexpression via beta arrestin. RELEVANCE (See instructions);Our research is aimed at identifying the signaling mechanism of regulation of the enzyme eNOS, which produces nitric oxide, the molecule of fundamental importance for vascular homeostasis. In particular we trying to identify the cellular factor responsible for maintaining eNOS in the optimal "coupled" state when It generates NO and not superoxide, which is a key mediator of endothelial dysfunction associated with diseases like hypertension. diabetes, atherosclerosis etc.